David Chase <chase@world.std.com> writes:> I'm a little curious about one thing -- does anyone, besides a> specifications- and-exact-correctness weenie like myself, actually> care about this level of detail in machine floating point?

Yes: people computing distributed physical models (physical
simulations, virtual reality, remote robot control), and like being
able to rely on programs doing identical computations in parallel and
getting the exact same result, instead of having to propagate
computation results from a centralized server through the network,
which can be VERY expensive in terms of latency, etc. Also, people who
need 100% reproducible results in their computations.

I'm not currently one of these people, but have been working with some
of them, who have been badly bitten by floating-point discrepancy
between JVM implementations in the past.

"Write Once, Run Anywhere"?
Without bit-exact correctness, it's but a shameful lie.

I agree that some people prefer faster approximate results, and should
be able to declare it for better performance -- but the default should
be to get exact (albeit possibly much slower) results.